The present invention relates to a packing tray substantially of cardboard or, for example, an extruded laminate containing these materials.
Packing trays which utilize cardboard or extruded laminates thereof are used to a very large extent as sales packings for fresh foodstuffs of almost any kind, and most often the packing tray is provided with a simple wrapping of cheap plastic film. When speaking of meat, poultry, and fish, the shelf life of such fresh goods is only very short, and according to present practice and rules, the sales period for ground meat is only one or two days. The sales period for sliced meat and fish is also only very few days, contributes to almost every supermarket necessarily having its own butchering department which is often not profitable at all based exclusively on turnover considerations.
GB-A-2 123 786 discloses a container in the form of a tray having a rim flange to which is heat-sealed a flexible first cover and a second cover of board material being attached to the first cover to strengthen the filled and sealed container. The second cover, which is preferably heat-sealed to the first, may have a window, and is removeable from the first cover without separation from the flange. The second cover may carry required printing instead of, as in many cases, put the sealed try inside a separate carton box simply to allow the outer carton to carry the required printing. However, by this known packaging container the sealing between the very thin first cover and the rim is only leakproof.
With this background, the invention has the purpose of providing an improved packing tray which may be a contributing factor for increasing, by way of example, the sales period for fresh foodstuffs, such as meat, ground meat, sliced meat and vegetables, poultry, salads and fish, and also may have other advantages.
The packing tray according to the invention has one press formed item, the upper side of which is a gas- and/or diffusion-proof coating having barrier abilities so that a covering film or a dome-shaped, e.g. transparent, lid may be connected in a gas-proof or diffusion-proof manner to the annular edge by welding, with the annular edge at the rounded corner parts being provided with bending lines, and the coating having a minimum thickness sufficient to ensure a smoothing and melting together of possible corrugations at the corner parts. By means of simple provisions there is hereby achieved a packing tray which is particularly suited for packing fresh foodstuffs, such as meat, minced meat, sliced meat and vegetables, poultry and fish, fruit, vegetables, salads, pasta, dinner dishes, bakery and dairy products. The packing tray makes possible the final top sealing of the packing tray and its content with simultaneous scavenging with a protective gas with the purpose of avoiding or reducing decomposition of the foodstuff, so that the keeping quality and hence the sales period of the foodstuffs concerned may be prolonged considerably.
The barrier qualities of the surface coating of the packing tray according to the invention together with the covering film and/or the lids provide a gas- and diffusion-proof barrier with a high barrier characteristic or with a low gas permeability. In practice, it is almost impossible to have a coating or a film covering completely impermeable to diffusion of aqueous vapour. Besides, in connection with meat, there is no real risk in practice of drying up as fresh meat gives off humidity However, it is of great significance to minimize diffusion of humidity out of the packing tray according to the invention.
In a simple way the tray according to the invention ensures that a final top sealing with tightness is achieved along edge parts of the rounded corner parts provided with bending lines that extend transversely to the edge parts. The thickness of the coating ensures, a smoothing of local unevennesses at corner parts because of the transversely directed bending lines, i.e. the thickness of the coating at the subsequent top sealing of the packing tray also contributes to improving the welding and/or melting (adhesion) together at the corner parts.
Advantageously, the packing tray according to the invention may be thus designed so that the covering film is a peelable film, i.e. a film which is exceptionally easy to remove from the annular edge of the packing tray.
With the purpose of making it very spacious, the packing tray according to the invention may advantageously be thus designed so that dome-shaped lids are used with a correspondingly designed, inverted tray, which trays are welded together edge to edge. In other words, the total packing consists of two identically shaped packing trays which are welded in a gas-proof edge to edges manner.
The packing tray according to the invention may be thus designed as sales packing in an advantageous way so that tray, lid and possible paper laminated extruded covering film are provided with printing.
Furthermore the packing tray according to the invention may be thus designed so that the tray is a single press formed item with the upper side of which between the cardbord and the upper weldable barrier coating provided with a susceptor coating. Thereby it is possible to achieve longer shelf life and at the same time a faster and more even cooking in a microwave oven.
The packing tray according to the invention may, by way of example, be used for prepared dinner dishes so that the tray is a single press formed item having a substantially round, elliptical or oval tray shape.
Furthermore, the invention concerns a method for making a packing tray out of sheet- or roll-shaped material layer of a cardboard material, which is laminated, coated or provided with coating by extrusion with the surface coating of material being weldable, which method punches the tray from blanks of material, the shape of which correspond to the packing tray, that preferably before punching have bending lines embossed at corner parts of the blanks of material, and that thereafter are press formed by means of a press forming tool, which is preferably a heated press forming tool. Any possible projecting material is cut off the annular edge of the finished packing trays.
The method according to the invention may advantageously be modified by using a material with a thick surface coating, which at the subsequent press forming by means of heat and/or friction, ensures a smoothing and melting together of the bending lines at the corner parts of the annular edge at least.
The invention also concerns a method for using a packing tray, for sales packing for foodstuffs, where one or more food items, e.g. a recently slaughtered chicken, is placed on the tray. The method covers the foodstuffs by a weldable, gas-proof film which is welded to the annular edge of the packing tray, preferably with simultaneous scavenging with a protective gas.
An alternative method for using a packing tray is, for example for sales packing of foodstuffs, where one or more food items, e.g. a portion of ground flesh or meat, is placed on the tray, wherein the foodstuffs are covered by means of a dome-shaped, transparent plastic lid which is welded to the annular edge of the packing tray, preferably with simultaneous scavenging with a protective gas.
A further alternative method for using a packing tray is, for example for sales packing for foodstuffs, e.g. prepared dinner dishes, where a portion of foodstuffs are placed on the tray, wherein the foodstuffs are covered by means of a dome-shaped lid of a correspondingly shaped, inverted tray, so that the trays are welded together at the annular edge, preferably with simultaneous scavenging with a protective gas.